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Overheating Subaru Forester / 2005 2.5 non turbo

I have a 2005 Subaru Forester with 88k on it. I bought it with about 70k on and have been doing a lot of the services myself.

I change the oil religiously . I recently changed the thermostat on the car, cleaned out the reservoir and now the car has new antifreeze. The reason I did this was because cars cooling fan is always going at full blast. This only started about 6,000 miles ago. So since it was a easy job I figured change the thermostat. I am in NY and it has been very cold out, but with my 10 mile commute to work by the time I pull into the parking lot the cooling fan is very loud and the noise is very noticeable.

I recently drove up to go skiing, ( the temp outside was 9 degrees) I was on the interstate going about 70 to 77 mph because the car was going uphill and the incline was significant , I would push more on the gas pedal and I would see the thermostat on the dash going up very closely to the red mark. I pulled over a few time, the fans were at full blast.

Can someone please advise on what I can do to fix this, water-pump maybe? And maybe this is normal ?

Thank you


Are you losing coolant? Is the heat inside the car working correctly? Do you see bubbles in your overflow tank? Any milky like consistency on your oil stick?

You could just have an air bubble in your system and it may need to be burped:
Park it on ramps, wait for it to cool, take the radiator cap off and start the car. Goose the engine a bit to about 1500 rpm. Use the throttle body lever so you can watch the coolant drop. You may see it drop and bubbles come out. When it drops and doesn’t come back to the level it was at, add some coolant. Do this until you don’t see it drop anymore.
Also, go to Subaru and get a bottle of coolant conditioner. It is said to make sure that you won’t have head gasket issues. It certainly seems to work, according to the experiences I’ve read. You just add it to your coolant.
While you’re there, get a new radiator cap. Subies are picky about their radiator cap. That could also cause overheating, once it is defective.

Hope it ends up something cheap. It very well may be but don’t let it overheat - ever!

@kmrbmw did you also replace the cap?
Are you losing coolant?
Have someone perform a “block test” to check if your headgaskets are blown.
Has your timing belt and waterpump been replaced yet?
When you replaced the thermostat, did you drain the radiator and the block also?

no coolant loss at all , i had the car on the lift last night, i looked underneath , even where the head gasket is, saw nothing , and the car was hot… The heat is pumping inside, nice and hot, no bubbles in the overflow tank too . I have not seen anything on the oil stick , i did change the oil last night so i will check it right now

Also after a 100 mile trip today to NJ , which was city , highway and highway uphill the temp gauge on the dash was dancing, even in city traffic the gauge was going up . it never hit the red but it was close.

i did not replace the cap
Are you losing coolant? No coolant loss at all,

Have someone perform a “block test” to check if your headgaskets are blown. ( Will do )
Has your timing belt and waterpump been replaced yet? ( No i have not, i thought this could wait till 100K )
When you replaced the thermostat, did you drain the radiator and the block also? I only drained where the thermostat is, after much reading i was said that the place where the thermostat is sufficient enough to get all the fluid out of the radiator

A failing water pump could cause these symptoms. There’s a slight chance the new thermostat isn’t working. I’ve experienced this myself. Did you test it in a pot of hot water to make sure it opens at the correct temp before you installed it? You might use an auto stethoscope (or just a piece of rubber garden hose or even just a thick wooden dowl making contact with the housing can be effective) and listen for any unusual noises coming from the water pump.